The present invention generally relates to centrifugal separators and more particularly relates to centrifugal oil filters for engine and vehicle applications.
Current heavy-duty diesel engines put a moderate amount of soot (a form of unburned fuel) into the oil pan. This soot is generated due to the fuel hitting the cold cylinder walls and then being scraped down into the oil sump when the pistons reciprocate in the cylinders. Up until recently, the nitrous oxide emission regulations in the United States and other countries have been high enough that the fuel injection timing could be such that the level of soot generated was not high. In typical applications, the soot level would be under 1% (by weight) of the engine oil at oil drain time. At these low levels, soot in the oil does not cause any significant wear problems.
Recently, there has been a move to significantly lower nitrous oxide emissions which requires much retarded fuel injection timing, which significantly increases the amount of soot being generated. At reasonable oil drain intervals, the soot level may be as high as 4 or 5% with retarded injection timing. When the soot level gets this high, lubrication at critical wear points on the engine becomes so poor that high wear results, significantly decreasing the miles to overhaul and causing high operator expense.
Thus, the engine manufacturer has two choices, suffer very high warranty costs and low miles to overhaul, or significantly lower oil drain intervals to keep high soot levels out of the oil. Neither of these choices is desirable, so there is a current strong need to have a means of getting the soot out of the oil, the subject of this invention.
A problem with removing the soot from oil is that it is very small in sizexe2x80x94around 0.1 to 2.0 micrometers. To remove such small particles from oil using barrier filtration is not feasible due to the large filter size required and the very high probability that the filter will become plugged very rapidly due to trying to filter to such a fine level.
One way that is feasible to remove the soot from the oil is by using a centrifuge, a device that removes the soot from the oil using centrifugal force. This type of device is used to separate blood constituents from blood and has many other applications in typical laboratory applications. The use of a centrifuge for an engine brings a requirement of doing it in a very inexpensive and reliable manner with the centrifuge being easily changed at oil change time. Heretofore, centrifugal filters have not been able to sufficiently remove soot from oil, sufficiently retain the soot, nor reliable enough for use in engine and vehicle applications.
It is a primary objective of the present invention to provide a practical and reliable apparatus for removing soot from engine oil.
It is another objective of the present invention to provide for inexpensive and easy maintenance of an oil centrifuge for use in engines of vehicles.
In accordance with these and other objectives, the present invention is directed at a disposable centrifuge cartridge adapted to be mounted in a cavity of a reusable cartridge casing (and the combination of the two which form a rotor of a centrifuge filter). The rotor is journalled via bearings to a centrifuge housing and is rotated about a predetermined axis to filter soot from engine oil from the engine of a vehicle. The invention includes a disposable cartridge which may made of plastic material which is supported and backed up by a reusable metal casing. The combination of using reusable and disposable elements in the rotor allows the cartridge to be built from less expensive and weaker materials such as plastic because the cartridge is backed up by the metal during high speed rotation at which force can be up to 10,000 times the force of gravity or more. The arrangement also provides for straightforward service maintenance in which the cartridge can be easily pulled out. and replaced.
Referring in greater detail to the cartridge, the disposable centrifuge cartridge is configured and dimensioned to be mounted in the cavity of the cartridge casing and being removable therefrom for replacement. The disposable centrifuge cartridge is closely dimensioned to the outer surface of the cavity such that the cartridge casing is adapted to be radially supported by the cartridge casing during operational rotation about the predetermined axis of rotation. The disposable centrifuge cartridge defines a filter chamber adapted to filter fluid that includes an entrance for receiving unfiltered oil, an exit disposed radially outward of the inlet to discharge oil and a deposit area disposed radially outward of the exit for trapping contaminants during rotation of the centrifuge rotor.
Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.